In-plane anti-phase vibration silicon micro-resonant pressure sensor and manufacturing method thereof

Abstract

The invention discloses an in-plane anti-phase vibration silicon micro-resonant pressure sensor and a manufacturing method, and relates to the technical field of micro-nano sensors, and the sensor structure comprises a frame, a pressure sensitive film and two double-end tuning fork resonators. Each double-end tuning fork resonator is composed of a tail beam, a supporting foot beam, an excitation beam and a vibration pickup beam, the two resonators are anchored to different positions on the diagonal line of the pressure sensitive film respectively, the pressure sensitive film drives the silicon island anchor points to move after bearing pressure loads, the silicon island anchor points transmit deformation to the resonators, the internal stress of the resonators is changed, and the vibration pickup effect is achieved. Therefore, the inherent frequency of the resonator is changed. The problems that a traditional H-shaped resonator can only work in an in-plane in-phase vibration mode, and energy loss is large during vibration are solved, shearing force and torque borne by the ends of the resonant beams can be counteracted, and the quality factor and working stability of a device are improved to a certain degree.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nano sensors, and more particularly to an in-plane anti-phase vibration silicon micro-resonance pressure sensor and a manufacturing method thereof. Background Art

[0002] At present, silicon micro-resonant pressure sensors convert changes in external pressure into changes in the resonant frequency of the resonator, and indirectly measure pressure by measuring frequency. They have the advantages of quasi-digital signal output, high sensitivity, strong anti-interference ability, and easy integration. They are very suitable for aerospace, industrial process control, and other precision measurement occasions that have strict requirements on accuracy and long-term stability. They have very wide applications and a huge market in military and civilian fields.

[0003] Most of the MEMS resonant pressure sensor products at home and abroad work based on electrostatic excitation / capacitive detection, inverse piezoelectric excitation / piezoelectric detection and electromagnetic excitation / electromagnetic detection. Among them, electrostatic excitation / capacitive detection has the advantages of non-contact excitation, mature technology and fast response speed, but the required driving voltage is relatively high, and due to the influence of parasitic capacitance, etc., small signals are not easy to detect. For the inverse piezoelectric excitation / piezoelectric detection method, its response speed is fast, which is conducive to the miniaturization and integration of sensors, but high-performance piezoelectric films are not easy to prepare. The resonant pressure sensor based on electromagnetic excitation / electromagnetic detection has the characteristics of simple structure and easy preparation, but the commonly used "H" type resonator can only work in the in-plane in-phase vibration mode, and there is a problem of large energy loss during vibration.

[0004] Therefore, there is an urgent need to develop a new resonant pressure sensor structure and manufacturing method to further improve the performance of MEMS devices. Summary of the invention

[0005] In view of this, the present invention provides an in-plane anti-phase vibration silicon micro-resonance pressure sensor and a manufacturing method to solve the problems existing in the background technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] An in-plane anti-phase vibration silicon micro-resonance pressure sensor, the sensor structure includes: a pressure sensitive film is designed inside a frame, two resonator structures, a central resonator and a side resonator, are arranged at the diagonal position of the pressure sensitive film, the resonator is connected to the pressure sensitive film through a silicon island anchor point, the resonator structure is composed of a tail beam, a support beam, an excitation beam and a vibration pickup beam, and the excitation electrode and the detection electrode are arranged on the resonator structure and connected to the lead-out electrode on the frame.

[0008] Optionally, the central resonator is located in the tensile stress region of the pressure sensitive membrane, and the resonance frequency increases with the increase of the pressure to be measured.

[0009] Optionally, the side resonator is located in a compressive stress region of the pressure sensitive membrane, and the resonance frequency decreases as the pressure to be measured increases.

[0010] Optionally, the pressure sensitive membrane is a square pressure sensitive membrane.

[0011] A method for manufacturing an in-plane anti-phase vibration silicon micro-resonant pressure sensor comprises the following steps:

[0012] S1. Prepare two double-sided polished silicon wafers, clean them by conventional standard process, and dry them with nitrogen;

[0013] S2, thermally oxidizing silicon dioxide on the surface of the silicon wafer to form an etching protection layer;

[0014] S3, photolithography of silicon island anchors on the front side of silicon wafer I, coating the back side with glue for protection, using buffered hydrofluoric acid to etch the silicon dioxide layer, using tetramethylammonium hydroxide-based etching solution to wet etch the silicon wafer to form silicon island anchors, and using buffered hydrofluoric acid to etch the silicon dioxide on the front and back sides;

[0015] S4, photolithography alignment mark mask pattern on the back of silicon wafer II, coating the front with glue for protection, and using buffered hydrofluoric acid to etch the silicon dioxide layer to form an alignment mark;

[0016] S5, silicon wafer I and silicon wafer II are hydrophilic treated, the front side of silicon wafer I and the front side of silicon wafer II are bonding surfaces, bonding alignment and pre-bonding are completed, and high temperature annealing is performed under nitrogen protection to achieve permanent bonding;

[0017] S6, the back side of silicon wafer I is thinned to the thickness of the resonator and polished;

[0018] S7, depositing insulating dielectric and metal film on the back of silicon wafer I in sequence, photolithography electrode mask pattern, etching the metal film using photoresist as mask to form electrodes;

[0019] S8, photolithography the resonator structure layer on the back side of silicon wafer I, using photoresist as a mask, sequentially dry-etching the insulating layer and the silicon structure layer until the bonding surface oxide layer is exposed;

[0020] S9. Photolithography the pressure-sensitive film mask pattern on the back side of silicon wafer II, and use the photoresist as a mask to dry-etch the oxide layer and substrate layer in sequence to form a pressure-sensitive film structure.

[0021] Optionally, the hydrophilic treatment uses a strong oxidizing wet cleaning solution or plasma.

[0022] Optionally, the metal film is one of Al, Ti / Pt, and Ti / Au.

[0023] It can be known from the above technical solutions that, compared with the prior art, the present invention discloses an in-plane anti-phase vibration silicon micro-resonant pressure sensor and a manufacturing method. The sensor structure includes a frame, a pressure-sensitive membrane and two double-ended tuning fork resonators. The double-ended tuning fork resonator is composed of a tail beam, a support beam, an excitation beam and a vibration pickup beam. The two resonators are anchored at different positions on the diagonal of the pressure-sensitive membrane. The pressure-sensitive membrane drives the silicon island anchor point to move after being subjected to pressure load. The silicon island anchor point transfers the deformation to the resonator, changes the internal stress of the resonator, and thus changes the natural frequency of the resonator. The present invention avoids the problem that the traditional "H" type resonator can only work in the in-plane in-phase vibration mode and has a large energy loss during vibration. It can make the shear force and torque on the end of the resonance beam offset each other, and to a certain extent improve the quality factor and working stability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0025] Figure 1 The figure is a schematic diagram of a three-dimensional structure provided by the present invention.

[0026] Figure 2 This is a local enlarged view of the central resonator provided by the present invention.

[0027] Figure 3 This is a local enlarged view of the side resonator provided by the present invention.

[0028] Figure 4 This is a schematic diagram of the local planed surface structure provided by the present invention.

[0029] Figure 5 This is a schematic diagram of the working mode of the resonator provided by the present invention.

[0030] Figure 6 This is a process flow chart of the resonant pressure sensor provided by the present invention.

[0031] In the figure: 1. Central resonator; 2. Side resonator; 3. Pressure sensitive membrane; 4. Frame; 5. Silicon island anchor point; 6. Tail beam; 7. Support beam; 8. Excitation beam; 9. Vibration pickup beam; 10. Excitation electrode; 11. Vibration pickup electrode; 12. Lead-out electrode; 13. Alignment mark; 14. Insulating medium. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The embodiment of the present invention discloses an in-plane anti-phase vibration silicon micro-resonance pressure sensor, such as Figure 1-Figure 4 As shown, the sensor structure includes: a pressure sensitive membrane 3 is designed inside the frame 4, and two resonator structures, a central resonator 1 and a side resonator 2, are arranged at the diagonal position of the pressure sensitive membrane 3. The resonator is connected to the pressure sensitive membrane 3 through a silicon island anchor 5. The resonator structure is composed of a tail beam 6, a support beam 7, an excitation beam 8 and a vibration pickup beam 9. The excitation electrode 10 and the detection electrode 11 are arranged on the resonator structure and connected to the lead-out electrode 12 on the frame.

[0034] Reference Figure 2 and Figure 3 For a resonator structure, due to the symmetry of the structure, any one electrode can be used as an excitation electrode 10 and the other electrode can be used as a detection electrode 11 to work normally.

[0035] Reference Figure 5 , the central resonator 1 and the side resonator 2 both work in an in-plane anti-phase vibration mode. In this mode, the shear force and torque on the end of the resonant beam of the resonator can offset each other, which can improve the quality factor and working stability of the device.

[0036] The working principle of the present invention is as follows:

[0037] The pressure sensitive film 3 drives the silicon island anchor 5 to move after being subjected to the pressure load. The silicon island anchor 5 transfers the deformation to the resonator, changes the internal stress of the resonator, and thus changes the natural frequency of the resonator. An excitation electrode 10 is arranged on the excitation beam 8 of the resonator. Alternating current is passed through the excitation electrode 10. The resonator vibrates due to the Lorentz force in the permanent magnetic field. The detection electrode 11 is arranged on the vibration pickup beam 9. When the resonator is in the working mode, the vibration pickup beam 9 vibrates in the opposite phase in the plane relative to the excitation beam 8. The detection electrode 11 cuts the magnetic flux lines in the magnetic field to generate an induced electromotive force, and the resonance frequency is picked up through the detection signal.

[0038] In a specific embodiment, the central resonator 1 is located in the tensile stress region of the pressure sensitive membrane 3, and the resonance frequency increases with the increase of the pressure to be measured.

[0039] In a specific embodiment, the side resonator 2 is located in the compressive stress region of the pressure sensitive membrane 3, and the resonance frequency decreases as the pressure to be measured increases.

[0040] The sizes of the central resonator 1 and the side resonator 2 do not necessarily need to be exactly the same, and the sizes of the tail beam 6, the support beam 7, the excitation beam 8 and the vibration pickup beam 9 can be modified as needed.

[0041] The shape of the lead-out electrode 12 can be set as required and does not have to be a square.

[0042] The double-ended tuning fork resonator design based on the tail beam 6 and the support beam 7 can make the resonator operate in an in-plane anti-phase vibration mode without modal crosstalk, so that the shear force and torque on the end of the resonant beam can offset each other, thereby improving the quality factor and working stability of the device.

[0043] The output signals of the center resonator 1 and the side resonator 2 are differentiated to improve the sensitivity of the sensor and compensate for the influence of temperature drift on the device performance.

[0044] In a specific embodiment, the pressure sensitive film 3 is a square pressure sensitive film.

[0045] A method for manufacturing an in-plane anti-phase vibration silicon micro-resonant pressure sensor, such as Figure 6 As shown, the following steps are included:

[0046] S1. Prepare two double-sided polished silicon wafers, clean them by conventional standard process, and dry them with nitrogen.

[0047] Preferably, the silicon wafer is a 4-inch N-type (100) silicon wafer with a thickness of 300 μm-500 μm.

[0048] S2, thermally oxidize silicon dioxide to 300nm-1μm on the surface of the silicon wafer to form an etching protection layer, such as Figure 6 As shown in (a) in .

[0049] S3, photolithography of silicon island anchor 5 on the front side of silicon wafer I, coating of glue on the back side for protection, using buffered hydrofluoric acid (BOE) to etch the silicon dioxide layer, using tetramethylammonium hydroxide (TMAH) based etching solution to wet etch the silicon wafer to form silicon island anchor 5, BOE to etch the silicon dioxide on the front and back sides, such as Figure 6 As shown in (b) in .

[0050] Preferably, the thickness of the silicon island anchor 5 is 5-10 μm.

[0051] S4, the back side of silicon wafer II is photolithographically aligned with the mask pattern, the front side is protected by glue, and the silicon dioxide layer is etched by BOE to form an alignment mark 13, such as Figure 6 As shown in (c) in .

[0052] S5, silicon wafer I and silicon wafer II are hydrophilic treated, the front side of silicon wafer I and the front side of silicon wafer II are bonding surfaces, bonding alignment and pre-bonding are completed, and high temperature annealing is performed under nitrogen protection to achieve permanent bonding, such as Figure 6 As shown in (d) in .

[0053] S6, the back side of silicon wafer I is thinned to the thickness of the resonator and polished, such as Figure 6 As shown in (e) in .

[0054] S7, the insulating medium 14 and the metal film are sequentially deposited on the back of the silicon wafer I, the electrode mask pattern is photolithographically formed, and the metal film is etched using the photoresist as a mask to form the excitation electrode 10, the pickup electrode 11 and the extraction electrode 12, as shown in FIG. Figure 6 As shown in (f) in .

[0055] In a specific embodiment, the insulating medium is silicon dioxide and silicon nitride, with a thickness of 300nm-1μm;

[0056] In a specific embodiment, the metal film is a common electrode material such as Al, Ti / Pt, or Ti / Au.

[0057] S8, photolithography of the central resonator 1 and the side resonator 2 on the back of silicon wafer I, using photoresist as a mask, sequentially dry-etching the insulating layer and the silicon structure layer until the bonding surface oxide layer is exposed, such as Figure 6 As shown in (g) in .

[0058] S9, photolithography the mask pattern of the pressure sensitive film 3 on the back of the silicon wafer II, and dry-etch the oxide layer and the substrate layer in sequence using the photoresist as a mask to form a pressure sensitive film 3 structure, such as Figure 6 As shown in (h) in .

[0059] In a specific embodiment, the thickness of the pressure sensitive film is 100 μm-150 μm.

[0060] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0061] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An in-plane anti-phase vibration silicon micro-resonant pressure sensor, characterized in that: The sensor structure comprises: a pressure sensitive film (3) is designed inside a frame (4); two resonator structures, a central resonator (1) and a side resonator (2), are arranged at the diagonal position of the pressure sensitive film (3); the resonator is connected to the pressure sensitive film (3) through a silicon island anchor point (5); the resonator structure is composed of a tail beam (6), a support beam (7), an excitation beam (8) and a vibration pickup beam (9); an excitation electrode (10) and a detection electrode (11) are arranged on the resonator structure and connected to an extraction electrode (12) on the frame.

2. The in-plane anti-phase vibration silicon micro-resonant pressure sensor according to claim 1, characterized in that: The central resonator (1) is located in the tensile stress region of the pressure sensitive film (3), and the resonance frequency increases as the pressure to be measured increases.

3. The in-plane anti-phase vibration silicon micro-resonance pressure sensor according to claim 1, characterized in that: The side resonator (2) is located in the compressive stress region of the pressure sensitive film (3), and the resonance frequency decreases as the pressure to be measured increases.

4. The in-plane anti-phase vibration silicon micro-resonance pressure sensor according to claim 1, characterized in that: The pressure sensitive film (3) is a square pressure sensitive film.

5. A method for manufacturing an in-plane anti-phase vibration silicon micro-resonant pressure sensor, characterized in that: The method for manufacturing an in-plane anti-phase vibration silicon micro-resonant pressure sensor according to any one of claims 1 to 4 comprises the following steps: S1. Prepare two double-sided polished silicon wafers, clean them by conventional standard process, and dry them with nitrogen; S2, thermally oxidizing silicon dioxide on the surface of the silicon wafer to form an etching protection layer; S3, photolithography of silicon island anchor points (5) on the front side of silicon wafer I, coating the back side with glue for protection, using buffered hydrofluoric acid to etch the silicon dioxide layer, using tetramethylammonium hydroxide-based etching solution to wet etch the silicon wafer to form silicon island anchor points (5), and using buffered hydrofluoric acid to etch the silicon dioxide on the front and back sides; S4, photolithography alignment mark mask pattern on the back of silicon wafer II, coating the front with glue for protection, and using buffered hydrofluoric acid to etch the silicon dioxide layer to form an alignment mark (13); S5, silicon wafer I and silicon wafer II are hydrophilic treated, the front side of silicon wafer I and the front side of silicon wafer II are bonding surfaces, bonding alignment and pre-bonding are completed, and high temperature annealing is performed under nitrogen protection to achieve permanent bonding; S6, the back side of silicon wafer I is thinned to the thickness of the resonator and polished; S7, depositing an insulating medium (14) and a metal film on the back of the silicon wafer I in sequence, photolithography an electrode mask pattern, and etching the metal film using the photoresist as a mask to form an electrode; S8, photolithography the resonator structure layer on the back side of silicon wafer I, using photoresist as a mask, sequentially dry-etching the insulating layer and the silicon structure layer until the bonding surface oxide layer is exposed; S9, photolithography the mask pattern of the pressure sensitive film (3) on the back side of the silicon wafer II, and sequentially dry-etching the oxide layer and the substrate layer using the photoresist as a mask to form a pressure sensitive film (3) structure.

6. The method for manufacturing an in-plane anti-phase vibration silicon micro-resonant pressure sensor according to claim 5, characterized in that: The hydrophilic treatment adopts a strong oxidizing wet cleaning solution or plasma.

7. The method for manufacturing an in-plane anti-phase vibration silicon micro-resonance pressure sensor according to claim 5, characterized in that: The metal film is one of Al, Ti / Pt and Ti / Au.

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